We recommend SparkPost as your email sending service for the CiviCRM platform, and even have developed an extension dedicated to such purpose: com.cividesk.email.sparkpost. It currently is one of the Top 10 most used extensions for CiviCRM.

This combination provides a reliable and managed SMTP-out service with DKIM-signed emails for improved deliverability, fully-integrated bounces handling, a graphical dashboard and control panel, all at a very affordable price.